The invention applies advantageously, but not limitingly, to battery-powered portable systems, in particular but not exclusively the remote terminals of wireless communication systems, for example cellular mobile telephones. Integrated systems for energy management in portable applications (battery operation) increasingly require different output voltages that are to be regulated, on the basis of an ever lower battery voltage.
A traditional approach includes creating a voltage regulated on the basis of the supply voltage with a linear regulator. This regulator uses an external capacitor to achieve its function. And use is made of as many linear regulators as outputs to be regulated. A drawback of this type of regulator is its low efficiency.
To alleviate this problem of low efficiency, use is made of switched-mode power supplies, also called “DC-DC converters”. The efficiencies are then close to SS to 90%, while under the same conditions, a linear regulator would have an efficiency of only 50%. However, a switched-mode power supply uses an inductive element in addition to a capacitor.
To regulate several outputs, it is conceivable to use several switched-mode power supplies. But this then presupposes the implementation of as many inductive elements, thereby increasing the cost and the surface area of the integrated circuit. Hence, the use has been envisaged of switched-mode power supplies capable of regulating several distinct outputs with a single inductive element. However, it is not always possible to retain a sufficient dynamic range between the various output voltages.
Additionally, contemporary switched-mode power supply systems do not make it possible to create, at output, regulated voltages with different signs. One approach for obtaining a positive voltage and a negative voltage includes using at least two linear regulators, with their aforesaid drawbacks, and a large number of external components.